In　order　to　investigate　the　effect　of　seasonal　temperature　on　microbial　community　structure　of　nitrification　biofilm　system,　the　nitrification　biofilm　system　in　MBBR　reactor　under　the　temperature　of　28.3,　23.3,　21.6,　9.6　and　-0.2　were　studied　by　using　denatures　gradient　gel　electrophoresis　polymerase　chain　reaction(PCR-DGGE)　technique.　The　activity　of　bacteria　affected　by　loss　of　the　water　temperature,　but　did　not　affect　stability　of　nitrification.　During　the　change　of　water　temperature(21.6~0.2),　the　total　bacteria　and　AOB　stayed　stable;　and　the　waste-water　treatment　of　Bacillus,　Flavobacterium　and　Nitrosomonas　also　stayed　stable.　The　dominant　bacteria　in　biofilm　mainly　was　Proteobacteria　and　Bacteroidetes　under　the　average　temperature　of　28.3~-0.2,　and　the　AOB　was　Nitrosomonas　that　was　the　part　of　β-Proteobacteria.　The　partial　nitrification　under　low　temperature　was　achieved　by　controlling　HRT　merely,　and　it　made　great　sense　for　the　application　of　shortcut　nitrification　process.　©　2017,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.